1. Field of the Invention
This invention relates in general to rotational vibrations in a storage device, and more particularly to a periodic rotational vibration check for storage devices to compensate for varying loads.
2. Description of Related Art
When it comes to data storage, more is never enough. Each time an increase in storage capacity is provided, new applications and uses for the increased capacity are developed, which leaves consumers and businesses needing even more. The advent of digital pictures, music and movies led to a greater diversity and capacity of storage systems and services. For example, consumers wanting to store more music, photos and videos look to the storage industry to pack more and more storage capacity on smaller devices.
Businesses' demand for storage also shows no signs of abating. E-mail and other reference demand for storage continues to be insatiable, particularly with the increasing importance and volume of e-mail, content-rich media and other reference data. In addition, the financial industry faces stringent requirements for data protection and retention, further increasing data volumes. Meanwhile, growing global competition has accelerated the need for improved business productivity, which require more frequent and intelligent access to transaction data. Such transaction data often must be protected and retained much longer.
Accordingly, the areal density needed to achieve today's demanded capacity points for magnetic and optical storage devices, such as disk drives tape drives, optical drives, etc., requires that data blocks be written with increasing accuracy relative to a track's center. External force or rotational vibration (RV) can cause a drive's head to deviate from the track center. Storage devices generate emitted vibration, given their mechanical nature. There are two sources of a drive vibration. Idle vibration occurs while the disk drive is spinning. Seek vibration occurs while the disk drive is seeking to a desired data position. Drives within a multi-disk enclosure are susceptible to the emitted vibrations of adjacent devices. Rotational Vibration (RV) is created when the vibration emitted from one or more disk drives operating in the enclosure induce vibration on adjacent drives. RV can cause increased seek times due to extended track settling time and results in an increased risk of an actuator traveling off track, thereby resulting in writes needing to be aborted or reads needing to be re-tried
As storage device technology advances, rotational vibration as described above begins to play an even greater roll in performance. Drive vendors have realized this and newer drives designs utilized robust mechanical structures and damping materials to reduce vibrations and prevent RV problems. For example, previous designs have utilized accelerometers that the drive uses to compensate for rotational vibration so that performance is not degraded. However, this actually creates an issue in storage enclosure systems because problems in the system design can be masked. As storage array densities increase, rotational vibration is induced from adjacent storage devices in the system so that the rotational vibration increases and becomes more load dependant. Seeks on drives produce the most amount of rotational vibration. Since different customers can be running unique loads, it is possible that a vibration level is hit that can cause data loss.
It can be seen that there is a need for a periodic rotational vibration check for storage devices to compensate for varying loads.